Stars Trails, Night Photography

60 1 minute pictures stacked together
16mm, f/2.8, ISO 6400, 60 x 1 minute

Last night we had new moon.
Best time to shoot stars and night sky. Month before I was not able to shoot stars for the simple reason - bad weather. Yesterday and today conditions seemed to comply. I had to take the chances.
Stars and sky are one thing but you also need some foreground interest in the frame. I checked what old ruins are available within 100 km radius of Vienna and are located on some hill. I really like this website http://www.ruine.at/. Very good source of information with coordinates and google maps links.

Things to consider when shooting stars and sky:

• You need dark place. Really dark place, 50-100 km away from large cities. Even the location from last night was not dark enough, there was small town below and it casted yellow tungsten lights. However this time I used to my advantage. I had old tower lit...
• Solid tripod. Has to be really solid as all frames will be shot with 30 seconds and more. Sometime even 16-30 minutes. 
• Wide angle lens, wider - the better.
• Cable release to be able to (A) - remotely shoot the frame, (B) - lock the shutter button when in BULB mode i.e. when shooting with times over 30 seconds.
• Intervalometer - handy tool to have when you can setup long exposures e.g. 16 minutes and you do not have to stand by the camera and monitor time. Also it will automatically shoot as many shots as you need with defined intervals. I used it last night.
• Some source of light...

Test image at ISO 25600, 8 sec, f/2.8

I arrived at the location around susnset to be able to scout the area before it became dark. I was looking for good spot overlooking North but having parts of the ruins in the frame, north star "does not move" and you can get nice circles around it.
Once I found my composition I only had to wait for the night. So having some drinks and smartphone is a god idea when it comes to killing time.
Around 9 p.m. I could start. Let's get into camera settings assuming we have the frame ready and camera is steady on the tripod.
To get most of stars lights the lens should be wide opened i.e. f/4 or f/2.8. Focus set manually to infinity. Now we have to calculate shutter speed. The best way is to pump-up ISO to max of the camera and set shutter speed to 10-30 seconds and make test shot and check the results.
Depending on the type of the shot you are after you will have to play with shutter speed and ISO. To get stars without trails you will be limited to 20-30 seconds before they trail. To get star trails exposure times can be anything from 4-8-16-32 minutes....or I will mention it in a bit.
But let's get back to setting exposure values.
Here's sample shot at ISO 25600 and 8 seconds exposure time. All shots have aperture of f/2.8.
I do not care about the noise and white balance. Sample above came right out of the camera. For the time being I am after stars shot and milky way. So I do not want any trails. Here comes the Rule of 600 which helps to calculate maximum shutter speed and get stars as stars and not trails.
Divide 600 by focal length of the lens = maximum number of seconds. In my case it was 600 / 16mm = 36 seconds.

Final Image
ISO6400, 36 sec, F/2.8

Now having test shot with 8 seconds at ISO25600 I can go down with ISO by 2 stops - 25600 minus 1 stop = 12800; minus 2nd stop - ISO6400 - at the same time I extend shutter speed - 8 sec times 2 = 16 and times two again - 32 seconds. I set manually to 36 get little bit more. So final shot was set at 16mm, f/2.8, 36 sec, ISO 6400. I used those settings for later shots as well.
Once I had my stars I moved to second part of the plan that is to shoot stars trails.
There are two ways to achieve the effect, the simplest way is to setup the camera to really long exposure times e.g. 16 minutes. In this case I would dramatically lower down ISO settings - to be more precise:

• 1 min - ISO 3200
• 2 min - ISO 1600
• 4 min - ISO 800
• 8 min - ISO 400
• 16 min - ISO 200

The problem with long exposure is noise. Camera's sensor becomes hot and produces more noise.
Alternative to this method is to shoot series of images and stack the together. In the end you get way more pictures with significantly less noise. The only problem is that they must be post processed. I used StarStaX software (freeware).

I shot series of 60 images, each one with 60 seconds exposure with no interval, so one after an another and achieved 1 hour exposure to get really long trails.

On the way I saw another good composition, unpacked all and took few more shots.
Here's one of them...
Staatz Ruins by night.
ISO 3200, f/2.8, 30 sec, 16mm

Cheers
Jerzy